[Federal Register Volume 59, Number 217 (Thursday, November 10, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-27852]


[[Page Unknown]]

[Federal Register: November 10, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration
14 CFR Part 39
[Docket No. 94-NM-123-AD]

 

Airworthiness Directives; Boeing Model 747 Series Airplanes, 
Excluding Airplanes Equipped with Pratt & Whitney PW4000 and General 
Electric CF6-80C2 Series Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 747 series 
airplanes. This proposal would require replacement of certain fuse pins 
on the upper link of the inboard and outboard struts. This AD also 
would require inspections to detect corrosion or cracks of certain fuse 
pins, and replacement, if necessary. This proposal is prompted by 
reports of cracked or corroded fuse pins on the upper link of the 
inboard and outboard struts, which could result in fracturing of the 
pins. The actions specified by the proposed AD are intended to prevent 
failure of the strut and separation of an engine from the airplane due 
to fracturing of the fuse pins.

DATES: Comments must be received by January 10, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-103, 
Attention: Rules Docket No. 94-NM-123-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. -
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: Tim Backman, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle 
Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, 
Washington 98055-4056; telephone (206) 227-2776; fax (206) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited -

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received. -
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket. -
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 94-NM-123-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs -

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-103, Attention: Rules 
Docket No. 94-NM-123-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion -

    The FAA received several reports of cracked fuse pins on the upper 
link of the inboard and outboard struts on Boeing Model 747 series 
airplanes. Several pins also showed evidence of corrosion. The fuse 
pins involved in these reports were ``bottle bore style'' fuse pins 
installed in the forward position of the struts. The cracking initiated 
in a machining groove in the inner recess of the pin bore, and it 
propagated due to fatigue. Cracking of the pins occurred on some 
airplanes as early as 9,366 total flight cycles (on the airplane) and 
42,493 total flight hours. One of the reports involved the complete 
fracture of both shear planes on the fuse pin; consequently, that pin 
had no load carrying capability. Analysis of several of the cracked 
fuse pins indicated that fracturing occurred in the recess area of the 
pin bore. -
    Corrosion may cause cracking of the fuse pins; this could lead to 
fracturing of the fuse pins. This condition, if not corrected, could 
result in failure of the strut and separation of an engine from the 
airplane. -
    The FAA has reviewed and approved Boeing Alert Service Bulletin 
747-54A2166, dated April 28, 1994, which describes procedures for 
replacement of ``bulkhead style'' and ``bottle bore style'' fuse pins, 
installed in the forward position of the upper link on the inboard and 
outboard struts, with either a 15-5 corrosion-resistant steel fuse pin 
(also known as a ``third generation'' pin) or a new bulkhead style pin. 
(This alert service bulletin specifies that installation of the third 
generation pin is preferred.) The alert service bulletin also describes 
procedures for repetitive detailed visual inspections to detect 
corrosion of the bulkhead style pins; magnetic particle inspections to 
detect cracks in these pins; and replacement of any cracked or corroded 
pin with a third generation pin or a new bulkhead style pin. -
    The alert service bulletin references Boeing Service Bulletin 747-
54-2155, dated September 23, 1993, as an additional source of service 
information for replacement of certain fuse pins, installed in the 
forward and aft positions of the upper link, with third generation 
pins. (Although there have been no reports of cracked pins in the aft 
position, replacement of the pin in the forward position with a third 
generation pin necessitates that the aft pin also be replaced with a 
third generation pin in order to preserve the function and location of 
the primary structural fuse.) -
    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require replacement of bottle bore style fuse pins, 
installed in the forward position of the upper link on the inboard and 
outboard struts, with either third generation fuse pins or new bulkhead 
style pins. This proposed AD also would require repetitive detailed 
visual inspections to detect corrosion of bulkhead style fuse pins; 
magnetic particle inspections to detect cracks in those pins; and 
replacement of any corroded or cracked bulkhead style fuse pin with a 
third generation fuse pin or with a new bulkhead style pin. 
Installation of a third generation fuse pin, if accomplished, would 
constitute terminating action for the inspection requirements of the 
proposed AD. The actions would be required to be accomplished in 
accordance with the alert service bulletin described previously. -
    The manufacturer has advised that it is currently developing a 
modification program for the engine strut that will positively address 
the unsafe condition addressed by this AD. Once this modification 
program is developed, approved, and available, the FAA may consider 
additional rulemaking.
    There are approximately 869 Model 747 series airplanes of the 
affected design in the worldwide fleet. The FAA estimates that 147 
airplanes of U.S. registry would be affected by this proposed AD. -
    It would take approximately 122 work hours per airplane to 
accomplish the proposed replacement of fuse pins with bulkhead style 
pins. The average labor rate is $60 per work hour. Based on these 
figures, the total cost impact on U.S. operators who replace fuse pins 
with bulkhead style pins is estimated to be $7,320 per airplane. -
    It would take approximately 140 work hours per airplane to 
accomplish the proposed replacement of fuse pins with third generation 
pins. The average labor rate is $60 per work hour. Based on these 
figures, the total cost impact on U.S. operators who replace fuse pins 
with third generation pins is estimated to be $8,400 per airplane. -
    It would take approximately 1.5 work hours per airplane to 
accomplish the proposed inspections (in addition to the work hours 
necessary for fuse pin replacement). The average labor rate is $60 per 
work hour. Based on these figures, the total cost impact on U.S. 
operators for the proposed inspections is estimated to be $90 per 
airplane per inspection. -
    The cost of required replacement parts would vary from airplane to 
airplane, depending upon the current airplane configuration. -
    The total cost impact figure discussed above is based on 
assumptions that no operator has yet accomplished any of the proposed 
requirements of this AD action, and that no operator would accomplish 
those actions in the future if this AD were not adopted. -
    The number of required work hours, as indicated above, is presented 
as if the accomplishment of the proposed inspection and replacement 
actions were to be conducted as ``stand alone'' actions. However, in 
actual practice, these actions, for the most part, would be 
accomplished coincidentally or in combination with normally scheduled 
airplane inspections and other maintenance program tasks. Therefore, 
the actual number of necessary additional work hours would be minimal 
in many instances. Additionally, any costs associated with special 
airplane scheduling would be minimal. -
    The FAA recognizes that the obligation to maintain aircraft in an 
airworthy condition is vital, but sometimes expensive. Because AD's 
require specific actions to address specific unsafe conditions, they 
appear to impose costs that would not otherwise be borne by operators. 
However, because of the general obligation of operators to maintain 
aircraft in an airworthy condition, this appearance is deceptive. 
Attributing those costs solely to the issuance of this AD is 
unrealistic because, in the interest of maintaining safe aircraft, 
prudent operators would accomplish the required actions even if they 
were not required to do so by the AD. -
    A full cost-benefit analysis has not been accomplished for this 
proposed AD. As a matter of law, in order to be airworthy, an aircraft 
must conform to its type design and be in a condition for safe 
operation. The type design is approved only after the FAA makes a 
determination that it complies with all applicable airworthiness 
requirements. In adopting and maintaining those requirements, the FAA 
has already made the determination that they establish a level of 
safety that is cost-beneficial. When the FAA, as in this proposed AD, 
makes a finding of an unsafe condition, this means that the original 
cost-beneficial level of safety is no longer being achieved and that 
the proposed actions are necessary to restore that level of safety. 
Because this level of safety has already been determined to be cost-
beneficial, a full cost-benefit analysis for this proposed AD would be 
redundant and unnecessary. -
    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment. -
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39 -

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment -

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES -

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 
106(g); and 14 CFR 11.89.


Sec. 39.13  [Amended] -

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Boeing: Docket 94-NM-123-AD.

    Applicability: Model 747 series airplanes; line numbers 1 
through 967 inclusive, and 969 through 992 inclusive; excluding 
airplanes equipped with Pratt & Whitney PW4000 or General Electric 
CF6-80C2 series engines; certificated in any category.

    Note 1: This AD does not require that the actions be 
accomplished on the struts of airplanes having straight bore fuse 
pins (installed on Model 747 series airplanes equipped with Pratt & 
Whitney PW4000 or General Electric CF6-80C2 series engines) or 15-5 
corrosion resistant steel (third generation) fuse pins.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent failure of the strut and loss of an engine due to 
corrosion or cracking of the fuse pins, accomplish the following:
    (a) For airplanes having bottle bore style fuse pins in the 
forward position on the upper link: Replace any bottle bore style 
fuse pin with a new bulkhead style fuse pin in the forward position, 
or with 15-5 corrosion resistant steel (third generation) fuse pins 
in the forward position, in accordance with Boeing Alert Service 
Bulletin 747-54A2166, dated April 28, 1994, at the later of the 
times specified in paragraphs (a)(1) and (a)(2) of this AD.
    (1) Prior to the accumulation of 5,000 landings on the fuse pin, 
or within 5 years since installation of the pin, whichever occurs 
first. Or
    (2) Within 6 months after the effective date of this AD.

    Note 2: Third generation fuse pins are installed in pairs (in 
the forward and aft positions). Therefore, replacement of an 
individual upper link fuse pin in the forward position with a third 
generation pin also would necessitate replacement of the pin in the 
aft position.
    Note 3: The alert service bulletin references Boeing Service 
Bulletin 747-54-2155, dated September 23, 1993, as an additional 
source of service information for replacement of the fuse pins with 
15-5 corrosion resistant steel (third generation) fuse pins. 
Installation of these third generation fuse pins is preferred over 
installation of bulkhead style fuse pins.

    (b) For airplanes having bulkhead style fuse pins in the forward 
position on the upper link: Perform a detailed visual inspection to 
detect corrosion of the pins, and a magnetic particle inspection to 
detect cracks, in accordance with Boeing Alert Service Bulletin 747-
54A2166, dated April 28, 1994, at the later of the times specified 
in paragraphs (b)(1) and (b)(2) of this AD.
    (1) Prior to the accumulation of 8,000 landings on the fuse pin, 
or within 8 years since installation of the pin, whichever occurs 
first. Or
    (2) Within 12 months after the effective date of this AD.
    (c) If no corrosion or crack is found during the inspection 
required by paragraph (b) of this AD, repeat the inspections 
thereafter at the intervals specified in paragraph (c)(1) or (c)(2) 
of this AD, as applicable.
    (1) For the inboard and outboard struts on airplanes other than 
those identified in paragraph (c)(2) of this AD: Repeat the 
inspections at intervals not to exceed 1,000 landings.
    (2) For the outboard struts on airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines: Repeat the inspections at 
intervals not to exceed 2,000 landings.

    Note 4: The outboard struts of airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines are equipped with thick 
wall ``4330 steel'' bulkhead style fuse pins in the forward position 
of the upper link. Crack propagation to critical length in these 
thick wall pins is slower than for pins installed on the struts of 
airplanes equipped with engines other than the Rolls-Royce RB211-
524G or -524H series.

    (d) If any corrosion or crack is found during any inspection 
required by this AD, prior to further flight, replace the corroded 
or cracked pin with either a new bulkhead style fuse pin in the 
forward position of the upper link, or with 15-5 corrosion resistant 
steel (third generation) fuse pins in the forward and aft positions 
of the upper link, in accordance with Boeing Alert Service Bulletin 
747-54A2166, dated April 28, 1994.
    (1) If the corroded or cracked fuse pin is replaced with a new 
bulkhead style fuse pin, prior to the accumulation of 8,000 landings 
on the new pin, or within 8 years since installation of the new pin, 
whichever occurs first, perform a detailed visual inspection to 
detect corrosion of the new pin, and a magnetic particle inspection 
to detect cracks of the new pin, in accordance with Boeing Alert 
Service Bulletin 747-54A2166, dated April 28, 1994. Repeat these 
inspections thereafter at the interval specified in paragraph 
(d)(1)(i) or (d)(1)(ii) of this AD, as applicable.
    (i) For the inboard and outboard struts on airplanes other than 
those identified in paragraph (d)(1)(ii) of this AD: Repeat the 
inspections at intervals not to exceed 1,000 landings.
    (ii) For the outboard struts on airplanes equipped with Rolls-
Royce RB211-524G or -524H series engines: Repeat the inspections at 
intervals not to exceed 2,000 landings.
    (2) If the corroded or cracked fuse pin is replaced with a 15-5 
corrosion resistant steel (third generation) fuse pin, no further 
action is required by this AD.
    (e) Installation of 15-5 corrosion resistant steel (third 
generation) fuse pins in the forward and aft positions of the upper 
link on the inboard or outboard strut constitutes terminating action 
for the requirements of this AD.
    (f) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Seattle Aircraft Certification 
Office (ACO), FAA, Transport Airplane Directorate. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector, who may add comments and then send it to the 
Manager, Seattle ACO.

    Note 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

    (g) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

    Issued in Renton, Washington, on November 4, 1994.
Darrell M. Pederson,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 94-27852 Filed 11-9-94; 8:45 am]
BILLING CODE 4910-13-U